This study deals with two aspects of goosefish red cells: (1) a -SH hemoglobin and (2) Copper II induced red cell aggregation. As the only marine teleost reported to have a hemoglobin that polymerizes, in vitro, by disulfide bond formation (Borgese et al 1988), goosefish hemoglobin would appear to be vulnerable to intracellular oxidation, polymerization and a reduced oxygen carrying capacity. Aside from its thermal instability (Borgese et all 1981), its high rate of auto-oxidation and its polymerization upon oxidation, little is known about the function, and structure of this hemoglobin or its possible role in protecting against oxygen toxicity. This investigation will address these issues by measuring (1) the activity and concentrations of the principal reducing systems of the cell (2) the effect of scavengers of oxygen radicals (3) factors regulating P50 and (4) determining the amino acid composition and primary sequence of goosefish hemoglobin. At concentrations of Cu== which have no effect on the red cells of other marine teleosts, elasmobranchs or invertebrates, goosefish hemoglobins are irreversibly aggregated. Preliminary observations, which suggest that one mechanism may be an unusual cross-linking by S-S bonds of externally oriented membrane proteins, will be pursued.